Schizophrenia, a debilitating disease that affects 1% of the world's population, is thought to be due to a complex interaction of genetic predisposition and environmental factors. The neurochemical basis for schizophrenia has long been thought to be a defect in the dopamine neurotransmitter system. Recent research has focused on an elevation in the density of dopamine D2 receptor which has been found in autopsy samples and in one recent positron emission tomography study. Based upon the recent availability of rat dopamine D2 receptor cDNA sequences, we have designed polymerase chain reaction primers to amplify segments of both rat and human dopamine receptor genes. Using these amplified DNA segments as probes for screening cDNA libraries and identifying restriction fragment length polymorphisms, we plan to subject the dopamine receptor hypothesis to intense scrutiny, and determine the inheritance pattern of putative schizophrenia genes.